Nonwoven film-type seaming elements for seaming woven and non-woven textiles are known. WO 2010/121360 (Manninen) discloses a seaming element for use in seaming an industrial textile. The seaming element is constructed and arranged to be affixed in a seaming position by being bonded to two of the substantially planar surfaces of the textile proximate the edges to be joined. The element includes first lateral edge region including an extension which defines both a longitudinal channel to accept a pin or pintle, and a plurality of apertures and land areas to allow for interengagement with a second seaming element at the second edge of the textile, and a second lateral edge which is to be bonded to the seaming edge of the textile. Various configurations of the seaming element are provided.
CA 2,749,477 (Manninen) discloses a profiled seaming element for use in an industrial textile where both the seaming element and the textile are each of profiled polymeric construction, e.g. formed from a slit and embossed film.
CA 2,762,349 (Manninen) discloses a seaming element that is constructed so as to provide two or more looped regions, thereby creating at least two channels across the seam, which allows for improved distribution of the tensile load across the element. The element can be constructed from two or more layers of polymer film, so that the same total element thickness can be obtained using thinner film, which allows for significantly improved biaxial orientation and thus maximization of the physical properties, in particular tensile strength.
It has been found that the ability to effect a consistent and reliably strong bond between the elements and the textile to which they are joined is directly dependent on the quality of the weld obtained as the element is bonded in place such as by a laser welding or similar technique. The lateral end regions comprising the legs or ends of the U-shaped element must be placed in intimate contact with the yarns or film to which they are to be bonded. Ideally, this contact extends over the entire surface of each individual yarn or textile component with which the element is in contact. During a laser welding process, for example, difficulties have been encountered with respect to applying a consistent pressure to the element as the weld is made to ensure its strength.
As shown in FIG. 1, the exterior surfaces of the exemplary seaming element of the prior art are flat. Where the seaming element is applied to a woven textile, the element is slipped over the yarn ends of the textile at its edge, for example in the manner shown in FIG. 2, prior to the welding process. The element is then pressed against the outside surfaces of the yarn ends as it is welded; a radiant energy absorbing material is located at the interface between the interior of the seaming element and the exterior of the yarn ends at the bonding region. A through-transmission laser welding process is used which allows the radiant energy of the laser to pass through the seaming element, for example, to the interface at which the radiant energy absorbing material is located. This material warms to the melting point of the yarns and seaming element and creates a weld between the two materials at their interface.
In certain instances, irregularities in the edge of a non-woven film textile, or the surface profile of yarn ends of a woven textile (e.g. the individual yarns are slightly twisted, or out of plane) do not allow for the desired intimate contact between the seaming element and film or yarns to be achieved. This lack of intimate contact can result in a weaker bond between the element and the textile. Following welding, the seam must be inspected closely to ensure that all bonds have been effectively made and the overall seam strength is reliable. This is difficult to determine and time consuming to do.
FIG. 1 is a perspective view of a prior art seaming element 100 which has a top surface 120, a bottom surface 121, a left edge (or end) 122, a right edge or end 124, a leading edge 126 and a trailing edge 128. The seaming element 100 further includes along its leading edge 126 a plurality of protrusions 150 between which are located notches 152. The notches 152 and protrusions 150 are dimensioned such that protrusions 150 on one seaming element 100 will fit into corresponding notches 152 on a second seaming element 100, to allow the two seaming elements 100 to be joined. The notches 152 extend into the body of the seaming element 100 from the leading edge 126 towards the trailing edge 128 a sufficient distance to allow corresponding protrusions from a second seaming element to be accurately located in the desired position within these notches. FIG. 1 is a perspective view of a seaming element 100 before being secured to an end or edge of a fabric to be seamed.
FIG. 2 is a cross-sectional side view of the seaming element 100 as it would be attached to a fabric 90. The fabric 90 includes a set of first (upper) warp yarns 103, and a set of second (lower) warp yarns 104, interwoven with weft yarns, comprising (smaller) first weft yarns 105, and (larger) second weft yarns 106. The fabric 90 has a first surface 123 upon which a product may be conveyed (corresponding to surface 120 of the seaming element 100) and a second surface 125 which in use will be in contact with the various moving and stationary elements of the machine for which it is intended.
The seaming element 100 is attached to the fabric 90 by inserting the warp yarns 103 and 104 into the interior of the U-shaped seaming element 100 at an end area of the fabric where selected weft yarns 105 and 106 have been removed. The warp yarns 103, 104 can be inserted in any suitable manner, but preferably the warp yarns 103 and 104 are cut evenly along the fabric edge, and several of the weft yarns 105 and 106 are removed from the fabric 90 to produce free ends of the warp yarns 103, 104 of a desired length. As shown in FIG. 2, these warp yarn free ends are then flattened and compressed to bring them together in the area 170, extending into the space within the seaming element 100 in such manner as to leave a channel 154 which is dimensioned to accept a pintle to secure the seaming element to a corresponding second seaming element to complete the seam. The warp yarn free ends are then affixed, for example by welding or bonding, at region 175 to the seaming element 100.
It will be appreciated that some of the warp yarns 103 and 104 in the region 175 may be mutually non-planar or otherwise misaligned and, in order to arrange them into a continuous and essentially homogenous planar array suitable for insertion into the area 170, it may be necessary to apply both heat and pressure to align them. The seaming element 100 must then be bonded such as by a laser welding process to this array so that a reliable and consistent bond is provided between the element and yarns. This is typically done using a so-called global ball or roller type laser which is passed over the exterior surfaces 120, 121 of the element 100. A through-transmission laser welding process is preferred for this purpose, and allows the exterior surfaces of the yarns 103, 104 in the area 170 to be securely welded to the interior of the seaming element 100. While an effective bond may be formed between a large proportion of the yarns 103, 104 and the element 100, there may be some for which only a partial weld is effected. These are difficult to detect but, because this bond must be reliably ensured (as it is critical to the successful operation of the textile), it is necessary to test or inspect a large proportion of the welds to ensure they are satisfactory. This is a time-consuming and tedious process for textiles having a typical width of between 3 m and 10 m, and the testing may not always be completely reliable.
Similar problems can also arise in relation to non-woven textiles, where any irregularity in the edges may reduce the effectiveness of the weld.
What is needed, therefore, is a mechanical means of assuring that a satisfactory bond is formed between the seaming element and the yarns or film in the welding process. In laser welding of materials such as plastics, pressure is usually an important parameter. Pressure aids heat transfer by conduction and aids fusion by forcing together the members to be welded. The laser can generate heat within the members to be welded without contact, however for an effective weld to be formed, it is necessary that the interface of the members to be welded be in as intimate contact as possible. It would be further desirable if such a means could be automated so as to minimize operator attention and intervention during the bonding process.
The present invention seeks to provide an economical and reliable method of manufacturing a seaming element, and a seaming element so produced which is constructed and arranged to ensure consistent high strength bonding of the element to the textile during the welding process.